JERUSALEM, May 26 (Reuters) - Pope Francis navigated the minefield of the Israeli-Palestinian conflict and humbly bowed to kiss the hands of Holocaust survivors on Monday, the last day of a successful Mideast trip laden with bold personal gestures.

"Never again, Lord. Never again!" he said in the dimly lit Hall of Remembrance in the Yad Vashem Museum which commemorates six million Jews killed by the Nazis in World War Two.

The fourth pope to visit Israel, Francis had earlier became the first to lay a wreath at the tomb of Theodor Herzl, seen as the founder of modern Zionism that led to Israel's foundation.

At the request of Prime Minister Benjamin Netanyahu, he also made an unannounced detour to Israel's "Memorial to the Victims of Terror", the day after unexpectedly praying at a towering Israeli security wall that is despised by Palestinians.

In a mirror image of the halt at the graffiti-smeared wall, Francis put both hands on the neat stone and marble monument and bowed his head, delighting his Israeli hosts who had smarted in silence over Sunday's impromptu stop.

"I pray for all the victims of terrorism. Please, no more terrorism," the softly spoken pope said at the memorial, which is engraved with the names of Israeli civilians killed mainly in attacks by Palestinian militants.

Netanyahu, standing at his side, thanked him for his words.

"We don't teach our children to plant bombs. We teach them peace, but we have to build a wall for those who teach the other side," he said, accusing Palestinian leaders of incitement.

Israel says its barrier in the occupied West Bank was erected to safeguard national security after a wave of Palestinian suicide bombings a decade ago. Palestinians see it as a brutal attempt to grab land they seek for a future state.

HUMBLE TRIBUTE TO HOLOCAUST VICTIMS

A day packed with political and religious encounters began at the gold-topped Dome of the Rock, the pope taking off his shoes before walking into the Jerusalem shrine from which Muslims believe the Prophet Mohammed climbed to heaven.

Francis then went to pray at the adjacent Western Wall, one the Jews' most revered shrines and a sole remnant of their sacred Second Temple, destroyed by the Romans in 70 AD.

There, he, a rabbi, and an Islamic leader - both friends from his native Argentina he invited to make the trip with him - embraced in a sign of the inter-religious dialogue that Francis is convinced can be a catalyst for peace in the region.

At Yad Vashem, the pope displayed the type of humility that has become his custom since being elected pontiff in 2013.

As he was introduced to six survivors of Nazi concentration camps and told of their stories of struggle and near-starvation, he bent slowly to kiss the hand of each elderly person.

Reading a haunting personal reflection that was a cross between a poem and a prayer, he called the Holocaust "a boundless tragedy" and "a great evil" that had shamed mankind.

The pope made one of his boldest political gestures on Sunday when he unexpectedly intervened in flailing diplomatic efforts to end the Israeli-Palestinian conflict, inviting the presidents from the two sides to his Vatican residence to pray for peace. The meeting is expected to take place on June 6.

The pope's spokesman, Father Federico Lombardi, said Francis had a strictly religious mission and "has no political agenda or proposals to make", but hoped the meeting could build trust.

"We hope it will encourage the revival of the process of peace, to give new courage, new inspiration to the people engaged in this process," he told reporters.

Both Mahmoud Abbas and Shimon Peres, who plays no decision-making role in Israeli diplomacy and leaves office in July, accepted the offer, which came just a month after U.S.-led peace talks collapsed amid bitter, mutual recrimination.

"We will work together, Jews, Christians and Muslims to bring an end to the conflicts," Peres said on Monday, speaking alongside the pope, a choir of children standing behind them.

However, there was little real hope that the unusual prayer meet could break decades of mutual mistrust, and Netanyahu, the key Israeli decision-maker, made no mention of the initiative.

Francis's final engagement saw him celebrating Mass in the Cenacle, a vaulted hall just beyond the walls of the Old City, which is revered by Christians as the room of the Last Supper.

The floor below contains what some Jews believe to be the tomb of King David, and Jewish extremists had protested in the area earlier this month, angry over plans by the government to give Christians regular prayer time at the site.

There were no demonstrations on Monday and at the end of the Mass, the pope flew down to Tel Aviv by helicopter and boarded his plane back to Italy. (Additional reporting by Dan Williams; Editing by Jeffrey Heller/Mark Heinrich)